The present invention relates to a method of producing sintered bodies having internal flushing medium channels and to an extrusion molding tool for implementing the method as well as a drilling tool.
European Patent Application No. 118,035 discloses a drilling tool having a metal drill bit holder on which is placed a sintered metal drill bit having at least one helical internal cooling channel. To manufacture the drill bit, it is proposed to use a bit blank having linear cooling channel recesses and, after sintering the blank under the influence of temperature, twist it to produce the desired helical cooling channels. This is done in that the helical cooling channels are produced by twisting the sintered metal blank as it leaves the extrusion molding device at an angular velocity which is adapted to the flow of material, the desired drill geometry and the pitch of the helix of the cooling channels, with care being taken to guide the sintered metal blank in a steady and axially uniform manner and also to make the twisting movement continuous and steady.
However, in practice, the hard metal drills produced in this manner exhibited cooling channels whose diameter and helical shape are irregular. The same problem occurs, in general, with other sintered bodies equipped with internal bores, particularly if such bores or not linear. As for the drilling tool, its manufacture requires additional twisting devices and appropriate control and regulating members.